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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Development of High-Speed Gas Bearings for High-Power Density Microdevices

[+] Author and Article Information
F. F. Ehrich, S. A. Jacobson

Gas Turbine Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139

J. Eng. Gas Turbines Power 125(1), 141-148 (Dec 27, 2002) (8 pages) doi:10.1115/1.1498273 History: Received December 01, 2000; Revised March 01, 2001; Online December 27, 2002
Copyright © 2003 by ASME
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References

Epstein, A. H., et al., 1997, “Micro-Heat Engines, Gas Turbines, and Rocket Engines—The MIT Microengine Project,” 28th AIAA Fluid Dynamics Conference, 4th AIAA Shear Flow Control Conference, Snowmass Village, CO, AIAA Paper No. 97-1773.
Epstein, A. H., Sentura, S. D., Waitz, I. A., Lang, J., Jacobson, S. A., Ehrich, F. F., Schmidt, M. A., Ananthasuresh, G. K., Spearing, M. S., Breuer, K. S., and Nagle, S., 1998, “Microturbomachinery,” World Intellectual Property Organization, International Publication Number WO 98/02643 and U.S. Patent #5,932,940.
Jacobson, S. A., 1998, “Aerothermal Challenges in the Design of a Microfabricated Gas Turbine Engine,” AIAA Paper No. 98-2545.
Breuer, K. S., Ehrich, F. F., Fréchette, L., Jacobson, S., Orr, D. J., Piekos, E., Savoulides, N., and Wong, C. W., 2000, “Challenges for Lubrication in High Speed MEMS,” NanoTribology, Stephen Hsu, ed., Kluwer, Dordrecht, The Netherlands.
Chen, K. S., 1999, “Materials Characterization and Structural Design of Ceramic Micro Turbomachinery,” Ph.D. thesis, Department of Aeronautics and Astronautics, M.I.T., Cambridge, MA.
Spearing, S. M., and Chen, K. S., 1997, “Micro-Gas Turbine Materials and Structures,” presented at 21st Annual Cocoa Beach Conference and Exposition on Composites, Advanced Ceramics, Materials and Structures.
Lin, C. C., Ghodssi, R., Ayon, A. A., Chen, D. Z., Jacobson, S., Breuer, K. S., Epstein, A. H., and Schmidt, M. A., 1999, “Fabrication and Characterization of a Micro Turbine/Bearing Rig,” MEMS ’99, Orlando, FL, Jan.
Fréchette, L. G., Jacobson, S. A., Breuer, K. S., Ehrich, F. F., Ghodssi, R., Khanna, R, Wong, C. W., Zhang, X., Schmidt, M. A., and Epstein, A. H., 2000, “Demonstration of a Microfabricated High-Speed Turbine Supported on Gas Bearings,” Solid-State Sensor and Actuator Workshop, Hilton Head Island, SC.
Protz, J. M., 2000, “An Assessment of the Aerodynamic, Thermodynamic, and Manufacturing Issues for the Design, Development, and Microfabrication of a Demonstration Microengine,” Ph.D. Thesis, Department of Aeronautics and Astronautics, M.I.T., Cambridge, MA.
Wong, C. W., 2001, “Design, Fabrication, Experimentation and Analysis of High-Speed Microscale Gas Bearings,” M. S. thesis, Department of Mechanical Engineering, M.I.T., Cambridge, MA.
Orr, D. J., 2000, “Macro-Scale Investigation of High Speed Bearings for MEMS Devices,” Ph.D. thesis, Department of Aeronautics and Astronautics, M.I.T., Cambridge, MA.
Piekos, E. S., Orr, D. J., Jacobson, S. A., Ehrich, F. F., and Breuer, K. S., 1997, “Design and Analysis of Microfabricated High Speed Gas Journal Bearings,” 28th AIAA Fluid Dynamics Conference, 4th AIAA Shear Flow Control Conference, Snowmass Village, CO, AIAA Paper 97-1966.
Piekos, E. S., and Breuer, K. S., 1998, “Pseudospectral Orbit Simulation of Non-Ideal Gas Lubricated Journal Bearings for Microfabricated Turbomachines,” ASME Paper No. 98-Trib-48.
Piekos, E. S., 2000, “Numerical Simulation of Gas-Lubricated Journal Bearings for Microfabricated Machines,” Ph.D. thesis, Department of Aeronautics and Astronautics, M.I.T., Cambridge, MA.
Ayon,  A. A., Braff,  R., Lin,  C. C., Sawin,  H. H., and Schmidt,  M. A., 1999, “Characterization of a Time Multiplexed Inductively Coupled Plasma Etcher,” J. Electrochem. Soc., 146(1), pp. 339–349.
Childs, D. W., 1993, Turbomachinery Rotor Dynamics, John Wiley and Sons, New York, Chap. 4 and 5.
Ehrich,  F. F., 1995, “Nonlinear Phenomena in Dynamic Response of Rotors in Anisotropic Mounting Systems,” ASME J. Vibr. Acoust., 118, pp. 154–161.
Breuer, K. S., 1999, personal communication.
Tang,  I. D., and Gross,  W. A., 1962, “Analysis and Design of Externally Pressurized Gas Bearings,” ASLE Trans., 5, pp. 261–284.
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Figures

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Schematic cross section of micro-bearing rig. The rotor is 4.2 mm in diameter and 450 μm thick (0.15 μm thick blades and 300 μm long journal bearing). The rotor is centered in a rectangular die structure with dimensions 15 mm×15 mm×2.3 mm. There are two semi-circular journal pressurization plenums that can be pressurized differentially to provide side-load.
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Schematic comparing generic types of gas thrust bearings
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Schematic comparing generic types of gas journal bearings
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Journal bearing etch test cross section
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Micro-bearing rig, exploded view
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Hydrostatic journal bearing natural frequency—macrorig (11)
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View of the rotor plate showing the 4.2-mm diameter microturbine with 150 μm tall stator and rotor blades, two symmetric speed bumps, and four pillars for the snap-off tabs. In this picture, the journal bearing gap has not been etched or the snap-off tabs severed.
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Operation of three microrig devices to high speed for sustained periods of time
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Measurement of journal and thrust-balance plenum flow rates in a microrig compared to the main flow through the turbine
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Frequency spectrum of the speed sensor signal as measured on the microrig. There is no way to distinguish whether this is indicative of a 6676 Hz or an 11,330 Hz precession frequency.
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Frequency spectrum of the speed sensor signal from an analytic model for Ωprecessionrotation=0.37 and 0.63 (identical result for both cases)
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Precession frequencies selected as possibly representative of the system natural frequency
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Amplitude response curves—peak amplitude without and with penetration into the regime of hydrodynamic stiffening from a simplified perspective
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Frequency response curve—peak amplitude with penetration into the regime of hydrodynamic stiffening in transcritical operation

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